Technology Science System of Pneumatics, or the Doctrinof Air  Alexander Hogg  c.1788

Hygrometer, Pyrmont Water, Thermometer.

Antique Copper engraving engraved by Eastgate, printed on hand made hemp and flax laid paper.

Published "According to an Act of Parliament" by Alexander Hogg, atthe Kings Arms No 16 Paternoster Row, London circa 1788

A hygrometer is an instrument used for measuring the moisture content in the atmosphere. Humidity measurement instruments usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed.

Pyrmont-Water, a celebrated mineral spring discovered at Pyrmont, in the Circle of Westphalia. It is of an agreeable, though strongly acidulated taste and emits a large portion of gas.

A thermometer is a device that measures temperature or a temperature gradient.

Condition= Excellent with no discolouring, foxing. Wearing along bottom edge, small tear to plate mark on the left edge.

Plate mark = 235 x 380